1. Field of the Invention
The present invention relates to a one-way valve for use with a medical device where it is desired to transfer fluid from a fluid source to a medical device or patent. More specifically, this invention is directed to prevent the backflow of blood or other medical fluid and to prevent the occurrence of excessively rapid flow infusion.
2. Art Background
The intravenous infusion of medical fluids in patients has long been recognized to be useful. However, certain problems related to intravenous infusions have persisted over the years.
A typical problem associated with intravenous infusion is the reverse flow of fluid into a cannula, such as a catheter tube or IV or IA needle that is inserted typically into a patient's vein or artery. For example, during the delivery of a solution to a patient through a cannula, one cannot predict accurately when the supply of IV solution become exhausted if the flow of the IV solution is generated by gravity. While this problem can be remedied by using a infusion pump which can be timed or by setting alarms to alert the personnel when an IV solution becomes exhausted, one still needs to solve the problem related to the difficulty in coordinating the availability of nursing personnel for disconnecting, at the right time, the soon-to-be-exhausted IV supply from the catheter tube or needle that is infused in the patient. Even where the supply of IV fluid does not become exhausted, the patient may raise the venipuncture location above the IV fluid source, thus, causing a reverse flow of fluid into the cannula (venipuncture meaning the place in the patient's vein or artery where a first tube is inserted). As a consequence of the problems enumerated above, the distal part of the cannula is affected by bleedback, and clotting in the cannula may result.
In a standard IV dispensing system where a fluid source is attached to the proximal end of a cannula, the flow of IV fluid into the cardiovascular system of the patient occurs because gravity exerts a force upon the IV fluid which exceeds the blood pressure in the cardiovascular system of the patient. When the IV fluid to be infused into the patient is low or exhausted, the difference between the IV fluid pressure and the patient's blood pressure, which initially drove the fluid down the cannula to the patient, changes so that the cardiovascular pressure prevails, giving rise to a blood backflow into the IV cannula. This backflow of blood contaminates the cannula such that within a short time, a clot may be formed in the cannula. As a consequence, an unacceptable risk arises that a clot may be introduced into the blood stream of the patient. It then becomes necessary to replace the catheter adding additional risk and expense to the medical care of the patient.
Several suggestions have been proposed to resolve the above-mentioned problem. Among these approaches, the closest to the present invention is a one-way outdwelling (outside the body of a patient) standard valve which prevents undesired blood flow into the distal end of an indwelling cannula. These approaches, however, do not have the advantages provided by the present invention.
For example, one such approach close to the present invention is an apparatus designed to prevent backflow due to pressure differentials. The "Nonreturn valve for medical uses," disclosed in the U.S. Pat. No. 3,601,151, issued to Winnard, discloses a one-way valve which, in one embodiment, is coupled between a needle inserted into a vein and a syringe used to withdraw blood samples. The valve member includes a body defining a void path through the valve, a bored stem constituting part of the path, and a chamber in which the stem is located and which is also part of the path. The stem portion is provided with a bore so that fluid passes into the chamber and through the valve. The stem part acts as a seat for the valve-closure member, which is an elastic sock which opens by expansion under the pressure exerted from the stem side of the valve. The elastic sock has a closed end about an inlet orifice of the stem, so that liquid must pass about the inner surface of the elastic sock closed end, and then move rearwardly about the orifice until the inner end of the sock is passed. The fluid then turns 180.degree. and flows along the outer surface of the sock outwardly on its path to the catheter. The valve is closed when the pressure is removed and the sock contracts under its own elasticity around the stem. In its neutral configuration, thus, the elasticity of the sock member seats the sock on the cylindrical surface of the stem, thereby preventing fluid flow through the stem. Reverse pressure forces the sock against the cylindrical surface, preventing flow in the reverse direction.
The disadvantage of the Winnard apparatus is that if the reverse pressure is high, the sock member may be subject to rupture. If a more resistant sock is provided, however, the valve will display less sensitivity to pressure differentials. Because the sock and stem might be specially sized for each particular bursting pressure, this type of valve is expensive to manufacture where valves of different bursting pressures are desired. Furthermore, this closed-end sleeve structure can shift and block an outlet orifice, possibly rendering the valve inoperative.
Bledsoe, U.S. Pat. No. 3,542,026, discloses a thoracostomy device to remove air and fluid from the area of the lungs through an elastic bulb having an air chamber connected by a tube to the pleural cavity to draw fluid from the cavity through the tube into the chamber of the bulb. At the inlet end of the bulb, a one-way valve is provided which closes the end of the tube as the fluid is discharged from the opposite end of the bulb. The Bledsoe device does not transport liquid, but only air.
Aine, et al., U.S. Pat. No. 4,858,209, discloses a miniature valve having the cantilever leaf spring disposed overlying an apertured plate for controlling the flow of fluid therethrough. An electrostatic potential applied between the cantilever leaf spring and the valve plate pulls the leaf spring over the apertured plate for variably controlling flow through the valve in accordance with the magnitude of the applied potential. Aine, et al.'s device uses an electrical current to open and close the valve.
Lashomb, U.S. Pat. No. 4,850,393, discloses an all-plastic check valve for a molded plastic surgical or medical device. A hollow cone-shaped or bullet-shaped stopper permits fluid flow in one direction, but in the back direction lodges against the ceiling ring or seat. The Lashomb device is structured differently and functions differently than the present invention.
Mittleman, U.S. Pat. No. 4,084,606, involves multiple sources of fluid and multiple paths of flow.
Mansca, '167, Adler, '831, Mittleman, '606, and Donowitz, et al., '327 patents disclose alternate flap valve configurations, while Szpur, '961, Ferrara, et al., '924, Brignola, '836, and Bark, '054 patents disclose other types of mechanical one-way valves that are not related to the configuration or design of the present invention.
There is a need, thus, for a better method and apparatus for preventing the backflow of blood into an intravenous or intra-arterial cannula and to prevent the occurrence of excessively rapid flow infusion which apparatus and method do not have the drawbacks of the prior art.